1. NATURE PLANTS | VOL 1 | APRIL 2015 | www.nature.com/natureplants 1
PUBLISHED: 7 APRIL 2015 | ARTICLE NUMBER: 15042 –15045
research highlights
ARCTIC ECOSYSTEMS
Tundra carbon gain
Glob. Change Biol. http://doi.org/2v7 (2015)
Deciduous shrubs are becoming increasingly
common in arctic tundra landscapes,
typically dominated by evergreens,
graminoids and cryptogams. This shift in
community composition could fuel carbon
uptake in these systems, according to a
one-year study of Alaskan tundra phenology.
Shannan Sweet, at Columbia University,
and colleagues compared the phenology
and productivity of two types of tundra in
Alaska — one dominated by evergreens
and graminoids and the other by
deciduous shrubs — using remotely sensed
measurements of canopy reflectance and
numerical models. Canopies dominated
by deciduous shrubs greened up faster,
and reached the period of peak greenness
13 days earlier, than canopies dominated by
evergreens and graminoids. As a result, the
peak season in the deciduous canopies lasted
an average of 10 days longer. Leaf area was
also greater in these ecosystems.
The deciduous canopies took up three
times more carbon over the course of the
growing season than the evergreen- and
graminoid-dominated canopies, due to the
longer peak season and increased leaf area;
peak season extension accounted for over
70% of this response. As such, the researchers
suggest that future increases in deciduous
shrub abundance in these systems could
enhance tundra carbon gain. AA
INSECT RESISTANCE
Triple whammy
Nature Biotechnol. 33, 301–305 (2015)
The brown planthopper (BPH) is a major pest
for rice production, causing up to 60% loss
of yield in affected crops. Multiple biotypes
and continuous evolution of BPH rapidly
circumvent conventional methods of pest
control. Instead, Yuqiang Liu, at the Nanjing
Agricultural University, and colleagues
have employed genes within a previously
reported resistance locus, Bph3, to induce a
broad-spectrum and an enduring defence
against BPH.
Rice varieties exhibiting insect resistance
due to the Bph3 locus have been used for
more than 30 years. Liu et al. used populations
derived from a cross between the resistant
rice variety Rathu Heenati and the susceptible
variety 02428 to map the Bph3 locus to a
79 kb region on chromosome 4, where four
genes (OsLecRK1–4) encoding lectin receptor
kinases were found. BPH-resistant lines had
an identical sequence for OsLecRK1–3 but
different sequences for OsLecRK4, indicating
that the three-gene cluster (OsLecRK1–3)
without OsLecRK4 represents Bph3. Indeed,
BPH infestation dramatically induced the
expression of OsLecRK1 and OsLecRK3 in
resistant plants but not in their susceptible
cousins, suggesting Bph3 increases the
resistance by enhancing the inducible
expression of lectin receptor kinases. This
hypothesis was verified in transgenic rice
lines over- or under-expressing the three
OsLecRK genes.
Introducing Bph3 into a susceptible
japonica variety, Ningjing 3, through
marker-assisted selection significantly
enhanced the resistance to BPH and white
back planthopper. The gene cluster thus
provides a valuable tool for breeding
rice with broad-spectrum and durable
insect resistance. JL
MEASURING CHLOROPHYLL
Looking-glass logic
Lab Chip 15, 1708–1716 (2015)
Wearable computing technology has begun to
be used in medicine to aid both training and
clinical practice, but fewer scientific uses have
been found elsewhere. Bingen Cortazar and
colleagues in the Department of Electrical
Engineering at the University of California
Los Angeles have employed Google Glass as a
flexible spectrophotometer for measuring the
chlorophyll content of leaves in the field.
The chlorophyll content of leaves is an
indicator of many aspects of both plant
health and the environment. Standard
assays destroy the leaf through chemical
extraction, need to be performed in a lab and
take time to yield results. Portable devices
exist to spectrophotometrically estimate
chlorophyll, but these are relatively expensive
and inflexible. With the UCLA team’s system
a leaf is put in a 3D-printed holder and
illuminated by LEDs powered by three AAA
batteries. Images of the leaf taken by Google
Glass worn by the experimenter are wirelessly
exported to a web-based application that
returns a value for chlorophyll content in
around ten seconds.
Cortazar et al. calibrated their system
against five species in the UCLA Botanical
Gardens and could immediately estimate
chlorophyll content from ten randomly
chosen and unrelated species. The Google
Glass system is not quite as accurate as a
specialist meter but its convenience, speed and
cost-effectiveness should make it an attractive
alternative, especially in remote locations. CS
Written by Anna Armstrong, Jun Lyu, Chris Surridge
and Guillaume Tena.
The innate immune system of higher organisms efficiently senses potentially dangerous
microbes by detecting foreign, conserved molecular patterns such as flagellin — part of the
flagellum present in many bacteria. In both plants and mammals this recognition is achieved
by membrane pattern recognition receptors (PRRs). In another example of independent
and convergent evolution, Stefanie Ranf and colleagues have identified the sensor for
lipopolysaccharide (LPS) in Arabidopsis, which is one component of the outer membrane of
Gram-negative bacteria.
LPS is also called an endotoxin because it induces a potent immune response in animals
that can lead to septic shock and death. In mammals, it is sensed by the receptor TLR4 —
a Nobel Prize winning discovery. The authors isolate a mutant, named lore, in which
LPS-induced calcium influx is abolished. The corresponding gene encodes a member of
the B-type lectin domain receptor-like kinase subfamily. It confers LPS responsiveness
by inducing downstream immune responses, making plants more resistant to bacterial
infection, and is responsible for LPS-triggered immunity.
LORE is restricted to the genomes of crucifers, including cabbages, oilseeds and cress.
However, when expressed in tobacco it confers LPS sensitivity, confirming that interfamily
transfer of PRRs can broaden the range of pathogen detection, like adding more antennas to
an air defence radar station, making this strategy of potential interest in crop engineering. GT
INNATE IMMUNITY
Septic shock Nature Immunol. http://doi.org/2v8 (2015)
RONNIEBRUGGE/ALAMY
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